The present invention relates to solar energy panels which gather and convert solar radiation into heat energy. With an evergrowing energy requirement and declining reserves of fossil fuels and oil, solar energy represents a currently comparatively unexploited source of energy which could lessen our dependence on the world's diminishing supply of organic fuels. Space and water heating occupy a significant portion of our total energy requirement; an efficient and economically viable utilization of solar energy for such heating purposes would greatly reduce our reliance on the world's declining organic fuel supplies.
Various types of solar energy panels have been previously developed to utilize the sun's substantially unlimited source of free energy. These prior designs have generally employed metal absorber plates to gather the sun's rays and transfer the resultant heat to an underlying layer of water. While the efficiency of a metal absorber plate is high, the cost of the metal of such a plate, and the milling costs make the use of such materials prohibitatively expensive for commercial purposes. Moreover, metal absorber plates suffer from corrosion and a large weight which make solar energy panels made of these materials commercially unacceptable.
Due to a low cost and low weight, plastics have also been investigated for use in solar energy panels. While these materials eliminate cost, weight, and corrosion problems, the efficiency of these materials as solar energy collectors is low. The efficiency of any solar energy panel depends directly upon the efficiency of the absorber plate in absorbing solar energy and transferring it to a body of heat exchange liquid.
With the low thermal conductivity of plastic materials, the use of absorber plates of plastic material produces a solar energy panel of low efficiency. An example of one such inefficient device is given in Stout et al, U.S. Pat. No. 3,918,430.
Coatings have also been developed in the prior art to increase the absorption of radiant energy. However, due to the low thermal conductivity of plastic materials, a plastic absorber plate will not efficiently transfer radiant heat from the absorptive coating to the heat exchange liquid. Moreover, these coatings suffer from a large cost and a low durability, rendering the commercial use of these coatings on plastic absorber plates unattractive.
The prior art, then, has been unable to develop a solar energy panel which is both efficient and commercially acceptable.